A 28-year-old woman with a 10-month history of gingival bleeding and a loose tooth was noted to have a gingival mass in the left side of her mouth. Her medical history was significant for depression, generalized fatigue, intermittent lower extremity weakness, and kidney stones. Examination revealed a 5 × 2-cm flesh-colored exophytic lesion on the leftlingual aspect of her mandible (Figure 1), as well as a loose tooth (No. 19). A panoramic x-ray film showed multiple osteolytic mandibular lesions and loss of the lamina dura surrounding the teeth (Figure 2). A tooth extraction was performed. Biopsy of the gingival mass revealed the pathologic findings shown in Figure 3. Diagnostic laboratory studies were performed.